/* CC0 (Public domain) - see LICENSE file for details */
#ifndef CCAN_BUILD_ASSERT_H
#define CCAN_BUILD_ASSERT_H

/**
 * BUILD_ASSERT - assert a build-time dependency.
 * @cond: the compile-time condition which must be true.
 *
 * Your compile will fail if the condition isn't true, or can't be evaluated
 * by the compiler.  This can only be used within a function.
 *
 * Example:
 *    #include <stddef.h>
 *    ...
 *    static char *foo_to_char(struct foo *foo)
 *    {
 *        // This code needs string to be at start of foo.
 *        BUILD_ASSERT(offsetof(struct foo, string) == 0);
 *        return (char *)foo;
 *    }
 */
#define BUILD_ASSERT(cond) \
    do { (void) sizeof(char [1 - 2*!(cond)]); } while(0)

/**
 * BUILD_ASSERT_OR_ZERO - assert a build-time dependency, as an expression.
 * @cond: the compile-time condition which must be true.
 *
 * Your compile will fail if the condition isn't true, or can't be evaluated
 * by the compiler.  This can be used in an expression: its value is "0".
 *
 * Example:
 *    #define foo_to_char(foo)                    \
 *         ((char *)(foo)                        \
 *          + BUILD_ASSERT_OR_ZERO(offsetof(struct foo, string) == 0))
 */
#define BUILD_ASSERT_OR_ZERO(cond) \
    (sizeof(char [1 - 2*!(cond)]) - 1)

#endif /* CCAN_BUILD_ASSERT_H */
